Molecules at the Electrochemical interface: Understanding Experiments with Simulations

The fundamental understanding of interfaces at the atomic level would greatly help in predicting the stability and reactivity of materials and eventually would lead to the rational tuning of the different components for example for heterogeneous catalysts, nano-electronics, photocatalysis.Most of the relevant processes in an electrochemical cell occur at solid/liquid interfaces. Unfortunately, the direct observation of these processes and the characterisation of the interfaces under operating conditions are still challenging for both experimental and modeling approaches. However, by developing efficiently scaling computational strategies, modelling of materials properties and processes from first principles is becoming sufficiently accurate as to facilitate the design and testing of new systems in silico. We present a few examples where computational materialsscience turns out to be valuable and necessary for developing novel functional materials.
In order to shed some light on selected functionalised electrochemical interfaces, we employ electronic structure calculations based on density functional theory, combined with the simulation of spectroscopic properties and with ab initio molecular dynamics (AIMD)[1]. In particular, we study the functionalisation of supported 2D materials, as hexagonal boron nitride (h-BN)[2], which modifies the interaction of adsorbing species on the metallic or semiconducting substrate, their reactivity, and spectroscopic signature[3]. We also show how the nanotexture of h-BN (corrugated vs flat by H-intercalation) affects these properties and how this can be related to the exfoliation of the functionalised two dimensional membrane. It has been shown that such a membrane can be employed for blue energy harvesting like osmotic power generation or ion separation[4]. Hence, AIMD simulations are carried out to understand the fluid structure and the dynamics at the interface with such 2D materials, with aiming at finding the relation between the electronic structure and the osmotic transport.
Furthermore, we aim at providing an atomic-scale description of the structural reorganisation of the water bilayer at different electrodes, as a function of applied voltage, and in the presence of adsorbates. We already concluded some preliminary work on the dynamic properties of the Pt(111)/CO/H2O interface [5], where we show how the water bilayer affects the chemical bonding of the of the CO molecules on the metal. In order to run these simulations we develop advanced sampling strategies, which allows long time scale simulations even for metallic systems and including explicit solvents.

1. Hutter, J., Iannuzzi, M., Schiffmann, F., VandeVondele, J. (2014). cp2k: atomistic simulations of condensed matter systems. Wiley Interdisciplinary Reviews: Computational Molecular Science, 4(1), 15–25.
2. Mertens, S. F. L., Hemmi, A., Muff, S., Gr¨oning, O., De Feyter, S., Osterwalder, J., Greber, T. (2016). Switching stiction and adhesion of a liquid on a solid. Nature, 534(7609), 676–679.
3. Muellner M., Balajka J., Schmid M., Diebold U., Mertens S.F.L. (2017). Self-Limiting Adsorption of WO3 Oligomers on Oxide Substrates in Solution. Journal of Physical Chemistry C, 121(36), 19743–19750.
4. Cun, H., Hemmi, A., Miniussi, E., Bernard, C., Probst, B., Liu, K., et al. (2018). Centimeter-Sized Single-Orientation Monolayer Hexagonal Boron Nitride with or Without Nanovoids. Nano Letters, 18(2), 1205–1212.
5. J. Lan, J. Hutter, and M. Iannuzzi; J. Phys. Chem. C 122, 24068 (2018).